Background: Culture based techniques are still the reference standard for diagnosis of Streptococcus pneumoniae but there are few limitations which still need to be addressed on priority. Antibiotic consumption by the patients before reporting to hospital is one of the major obstacles in diagnosis of Streptococcus pneumoniae cases by culturing technique and may be under reporting of cases. So along with microbiological, molecular based methods can be used as for diagnosis of actual Streptococcus pneumoniae cases. Here a prospective study is conducted where both culture and PCR based approaches are applied for identification of S. pneumoniae cases.
Methods: Nasopharyngeal swabs and also blood samples are collected from clinically diagnosed patients for culturing and DNA isolation. Microorganisms obtained after positive blood culture and from nasopharyngeal swabs are identified using MALDI- TOF and by 16s rRNA gene sequencing. 16s rRNA gene sequencing is also performed from DNA of blood samples used for culturing.
Results: Out of 9 nasopharyngeal isolates, 1 identified by culturing and MALDI-TOF as Streptococcus pneumoniae, whereas second isolate was identified as Streptococcus species by MALDI-TOF. However both isolates confirmed as Streptococcus pneumoniae with 16s rRNA gene sequencing. From 10 blood samples which were reported sterile in blood culture, surprisingly, we were able to amplify 16s rRNA gene from 06 samples indicating presence of bacterial genetic material in these sterile blood samples. Sequencing for identification of pathogens from these samples is going on.
Conclusion: Molecular approach, in addition to culture based identification, may further improve diagnosis of Streptococcus pneumoniae cases.